Video streams are typically encoded in compression with packetization when transmitted over packet-switched networks such as the Internet, enterprise virtual private networks (VPNs), and service provider Internet Protocol Television (IPTV) networks. Video codec specifications such as ITU-T H.264 and H.263 define the packet formats to carry the encoded video data in slices, where the payload headers contain the slice types of video data in the payloads. Thus, network devices in the middle may be able to distinguish the more important packets from the less important by packet markings or deep packet inspection (DPI) when packet drops are needed in a network queue upon congestion or for congestion avoidance.